1. Field of the Invention
This invention relates to steam and water drums, and more particularly, to means for visually observing the operation of the internals of a steam and water drum.
2. Description of the Prior Art
The importance in steam generation of providing clean dry steam has long been recognized, and as the operating pressure and capacities of steam generators have markedly increased, the need for removal of moisture and impurities from the steam to a greater degree has become more important to avoid harmful deposits in the associated superheater and/or turbine. Moreover, the functional nature of a steam and water drum is such that two fluid phases co-exist at a saturation temperature corresponding to the pressure in the drum. Therefore, the task of separating the entrained liquid droplets, i.e. moisture, from the vapor phase has generally been approached as a problem of mechanical separation. Various separating devices such as cyclone separators, flow directing baffle arrangements or scrubbers and a combination of these devices have been used to separate the relatively heavy moisture droplets and the impurities therewith from the vapor. For example, in a modern drum boiler the separation of steam from the moisture delivered by the steam water risers usually takes place in two steps. The first step, or primary separation, generally performed by cyclone type separators, removes nearly all the water from the mixture, so that, in effect, no steam is recirculated to the heating tubes. Secondly, secondary separators, e.g. steam scrubbers, removes substantially all solid contaminents from the steam such that the steam is sufficiently pure for use in high pressure turbines.
A performance analysis, however, of these steam and water drum separating devices in an operating steam generator system has generally been limited to long and arduous indirect test procedures. Accordingly, it is desirable to directly examine the effectiveness of the separating equipment, that is, to visually observe the performance of the equipment during operation and to actually see and/or visually record whether moisture, or water droplets, are being carried along with the issuing steam.
Furthermore, although abnormally high water levels produced from operational upsets, or "priming", or high concentrations of solids which produce foaming within the drum are comparatively rare occurrences in modern steam generation systems, it is also desirable to observe the water level surface conditions within the drum. In addition, water flow into and out of the drum may produce water level disturbances which are not readily discernable by any other means other than visual observation.
Accordingly, a visual observation device capable of operation within an operating steam and water drum, and capable of permitting visual observation of both the steam separating devices and the water level conditions of the drum is desired.
Attempts to view the internals of a steam drum by use of sight glasses and observation ports commonly known in the art have generally been frustrated by fogging of the sight glass window or port due to vapor condensation thereon. Furthermore, the field of vision available to these viewing windows was generally limited to a very narrow angle due to size considerations and location.
Therefore, there is a need to provide industry with a visual observation device capable of operation in a steam and water environment such as found in an operating steam and water drum for viewing the effectiveness of the internal equipment and the water level conditions within the drum.